This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the subject matter described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, not as admissions of prior art.
Solder is used to electrically and mechanically connect electrical components of downhole tools. For instance, solder can be used to join metal components, such as for connecting an electronic component, such as a microchip, controller, or multi-chip module, to a circuit board, such as a printed wiring board (PWA). Eutectic tin-lead solder has long been used for its reliability, availability, and cost effective advantages. For instance, some tin-lead solders may have melting points as high as 300 degrees centigrade (C). However, the Restriction of Hazardous Substances (RoHS) banned lead from electronics, thereby creating a need to develop lead-free alternatives to tin-lead solders.
Some attempts at finding alternatives for high temperature applications focused on tin-silver-copper alloys (also known as Sn—Ag—Cu alloys, or SAC alloys). SAC alloys typically have a melting point of between approximately 217 and 221 degrees C. However, as the melting point of SAC alloys is lower than traditional lead-based solders, their reliability becomes questionable under certain harsh environmental conditions, such as in drilling conditions where high temperature thermal fatigue is combined with high instances of mechanical shock and vibrations.
Subsequent attempts increased the silver content to reduce the creep rate of the SAC solder and thereby increase reliability when subjected to temperature aging and cycling. However, the long-term reliability of SAC alloys with high silver (Ag) content is also questionable under harsh environments, such as those inducing high temperature thermal fatigue and mechanical shock.
Accordingly, a lead-free solder having improved thermal and mechanical performance properties when compared to SAC alloys would be highly desirable.